Unfortunately, ALL modern-day IDEs are memory eaters, and 440MB is on the low side. I was suffering until I upgraded my total system RAM from 1GB up to 2GB - although the email client app I run is also a memory hog.
Additionally, when you're debugging, there's the overhead for debugging and in the case of debugging webapps, the overhead for the webapp server that the debugged application is running in.
Eclipse should not be calling specifically for non-virtual memory, but it will run really slow if it doesn't have enough physical memory.
An IDE is no substitute for an Intelligent Developer.